1. Field of the Invention
The present invention relates to a lithographic apparatus and a device manufacturing method.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate (e.g., a workpiece, an object, a display, etc.). The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays, and other devices involving fine structures. In a conventional lithographic apparatus, a patterning means, that is alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device), and this pattern can be imaged onto a target portion (e.g., comprising part of a die, one die, or several dies) on a substrate (e.g., a silicon wafer or glass plate) that has a layer of radiation-sensitive material (e.g., resist). Instead of a mask, the patterning means can comprise an array of individually controllable elements that generate the circuit pattern. Lithographic systems utilizing such arrays are generally described as maskless systems.
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include steppers, in that each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and scanners, in that each target portion is irradiated by scanning the pattern through the beam in a given direction (the “scanning” direction), while synchronously scanning the substrate parallel or anti-parallel to this direction.
The product pattern to be created on the substrate can be defined using a vector design package, according to a Graphic Design System II (GDSII) format, for example. In a maskless system, the output file from such a design package is processed to derive a control signal that is sent via a data path, which can comprise further processing stages, to the array of individually controllable elements. The control signal contains information to manage switching of each element of the array of individually controllable elements for each flash of the radiation to be patterned by the array (typical strobe frequencies being in the region of 50 kHz for this application). The bandwidth required to transfer such a volume of data can be enormous. The situation worsened by the data conversion and optimization processing that takes place in the data path (i.e., between the output file and the array of individually controllable elements). These data processing steps are often implemented during imaging (to avoid having to store vast volumes of data off-line and to allow response to changes in apparatus conditions) and require access to portions of the data being transmitted to the array of individually controllable elements. High speed processing means and further high bandwidth connections need to be incorporated into the data path to accommodate the abovementioned data processing leading to further increases in costs and/or limits on the speed and accuracy with which the requested image can be written to the substrate.
Therefore, what is needed is a lithography apparatus and device manufacturing method that makes more efficient use of the bandwidth available in the data path in maskless lithography systems.